This invention relates to air conditioners and heat pumps and in particular to self contained packaged air conditioner and heat pump units which include both indoor and outdoor coils and a pair of blowers.
Conventional packaged air conditioners and heat pumps generally include both a conventional centrifugal blower for the indoor heat exchanger and an axial blower for the outdoor heat exchanger. All conventional packaged terminal air conditioners also include some type of dividing wall which divides the indoor portion of the unit from the outdoor portion of the unit. Air is conventionally drawn into the unit through the sides, the rear, the outside face, or the bottom of the unit and is blown out of the unit after passing over the heat exchangers.
Some prior art air conditioners have included tangential or cross flow blowers for the indoor heat exchanger. U.S. Pat. No. 4,478,053 discloses an air conditioner which includes two vertically mounted cross flow blowers, one of which is used to move air across the indoor heat exchanger and the other which is used to move air across the outdoor heat exchanger. This patent shows a dividing wall for separating the two blowers comprising a complicated hollow double walled structure to permit ventilation. Separate rounded parts provide scrolls for the blowers. Other prior art air conditioners have used centrifugal or axial flow blowers.
Several problems have been encountered with the prior art air conditioners with axial flow fans and centrifugal blowers described above. One of the problems is that the air flow through or across the heat exchangers is non-uniform due to the nonuniform performance characteristics of prior art blowers whereby hot spots develop in the heat exchangers, thus causing the heat transfer process to be less efficient than desired.
Another problem with these prior art air conditioners has been that they are rather noisy. The noise is primarily created by the air flow through the unit because prior art centrifugal or axial flow blowers generate substantial expansion and contraction of the air and cause impact of the blower blades upon the air. Such noise is particularly undesirable as packaged air conditioners are commonly used in dwelling places, either by mounting through a wall or in a window.
Another problem with prior art self contained air conditioners has been that, due to the types of blowers used, the depth dimension of the unit is much greater than is desired. Thus the prior art units tend to take up much more space in the dwelling than is desired.
U.S. Patent Nos. 3,200,609 (Laing) and 3,301,003 (Laing) disclose air conditioners which use two cross flow blowers. Both of these patents disclose air conditioners with various arrangements of the evaporator and condenser coils and of the cross flow blowers. Each side of the air conditioner has a heat exchanger coil in communication with the indoor or outdoor air, respectively. Cross-flow blowers are positioned in respective interior regions for inducing air flow through approximately half of the heat exchanger and for forcibly blowing air through the other half of the heat exchanger. The respective interior regions are located on opposite sides of a divider wall which includes additional curved wall portions for guiding the flow of air away from the respective cross-flow blower. The air conditioner design of Laing reduces the width of the air conditioner by positioning the cross-flow blowers in a vertical stacked arrangement. However, many problems exist with the air conditioner of Laing.
One problem with the Laing air conditioner relates to its air intake arrangement. A grill covers the intake section of the heat exchanger. Visually, a grill covering is much less attractive than a solid panel. Functionally, such a large grill is more likely to take air in which was exhausted from the air conditioner thereby setting up a closed loop of air flow. Further, a grill only partially protects the interior contents of the air conditioner. In addition, to hold the grill against the filter in the Laing air conditioner, an extra apertured backing is provided, and the grill pivots to allow access to the filter. However, providing a structurally sound pivot increases the cost of the air conditioner.
An additional problem with the Laing air conditioner involves the air flow. Each blower induces air flow through one section of its heat exchanger and forces air out a second section of its heat exchanger. This creates a first induced air stream which is at a different temperature than a second forced air stream. However, the same heat exchanger interacts with both air streams, so that the heat exchange is less efficient than in a structure wherein all the air passing through the heat exchanger is at the same temperature. A further inefficiency caused by the air streams is that the fan discharge air stream has a non-uniform velocity which can cause hot spots, and ameliorating this problem requires that additional flow channeling cowlings be positioned between the blower and the heat exchanger and requiring the fan to operate at a higher RPM. This higher RPM can cause further noise.
Still another problem with the air conditioner of Laing involves the number of dividing wall pieces required to form the indoor and outdoor compartments of the air conditioner. One partition wall is needed to separate the indoor compartment from the outdoor compartment, and each compartment requires additional wall structures, including one guide wall and one curved portion. Additional pieces would also be required for causing a more uniform flow of blown air through the heat exchanger as mentioned above. The numerous additional parts increase the difficulty of assembly, and each additional part creates a possibility of noise generation by a loose or degenerated attachment.
A further problem with the air conditioner shown in Laing is an unsatisfactory handling arrangement for condensate. Condensate is collected in the sump and from there is picked up by a fibrous belt to be carried to the top of the air conditioner. The condensate water drops onto the blades of the blower rotor so that the water is broken up into tiny droplets which are then carried off in the warm air stream passing from the blower to the heat exchanger. While this arrangement is satisfactory when the air conditioner is used in the cooling mode, in the heating mode an arrangement must be provided to prevent condensate from the outdoor coil from being returned to the outdoor coils where it could freeze and reduce the capacity of the unit. In some prior art air conditioners, a drain valve has been provided which normally opens in cold weather to allow the condensate to drain off so that the condensate does not get thrown back onto the cold coil.
A further problem of the prior art air conditioners has been that they have used a substantial number of parts in order to provide the indoor and outdoor compartments and the blower scrolls, thereby adding expense to such units. A conventional design of a packaged air conditioner with a centrifugal indoor blower and a axial outdoor fan has seven basic components, namely a blower scroll, blower orifice, blower discharge deck, divider wall, divider wall cover, condenser fan orifice, and condenser fan shroud. Considering that each basic component requires additional parts and fasteners, the assembly of a package air conditioner can become quite time consuming and costly.
It is therefore desired to provide a self contained packaged air conditioning unit wherein the air intake arrangement is visually and functionally pleasing, wherein the filter can easily be accessed with minimum cost, wherein the entering and exiting air flows are separated, wherein the flow of air through or across the heat exchangers is uniform, wherein the speed of the air flow through the unit is relatively low thereby causing the unit to be quiet, wherein the depth dimension of the unit is much less than in conventional units, wherein the blowers are driven more reliably and efficiently, and wherein the number of parts used in constructing the unit is much smaller than in conventional units.